The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Advances in plasma processing have facilitated growth in the semiconductor industry. During plasma processing, diagnostic tools may be employed to ensure high yield and reliability of devices being processed. Optical emission spectroscopy (OES) may be used as a diagnostic tool for gas-phase monitoring of etchants and etched products to maintain control of process parameters.
Plasma has optical emission spectral characteristics that are a function of multiple variables including, but not limited to, constituent gas species, pressure, energy density, driving power, and the like. The optical emission spectrum of plasma includes, but is not limited to, deep ultra-violet (UV) through far infra-red (IR) wavelengths, and may be observed using a spectrometer.
Optical monitoring of plasma may be performed by collecting an optical emission spectrum via a collimator through a quartz window of a plasma etch chamber. The spectral information, transmitted via a collector fiber optic bundle, may be measured by the spectrometer. With the spectral information from the optical monitoring, a considerable amount of information relating to constituent species may be collected and analyzed to provide guidance for process monitoring and control during plasma processing.